Integrated thermoelectric honeycomb core and method

ABSTRACT

The disclosure provides a thermoelectric composite sandwich structure with an integrated honeycomb core and method for making. The thermoelectric composite sandwich structure comprises two prepreg composite face sheets and an integrated honeycomb core assembled between the face sheets. The honeycomb core comprises a plurality of core elements bonded together with a core adhesive. Each core element has a first side substantially coated with a negative Seebeck coefficient conductive material having a plurality of first spaced gaps, and each core element further has a second side substantially coated with a positive Seebeck coefficient conductive material having a plurality of second spaced gaps. The honeycomb core further comprises a plurality of electrical connections for connecting in series the first side to the second side. A temperature gradient across the honeycomb core generates power.

BACKGROUND

1) Field of the Disclosure

The disclosure relates generally to devices and systems for generatingelectrical power, and more particularly, to thermoelectric devices andmethods for generating electrical power.

2) Description of Related Art

Small sensors are used in a variety of applications in aircraft,spacecraft, motorcraft, watercraft, and other craft, as well as vehiclesand structures. For example, an array of small sensors may be used instructural health monitoring (SHM) to continuously monitor structures,such as composite structures of aircraft, and measure materialcharacteristics and stress and strain levels to assess performance,possible damage, and current state of the structure. A series of smallsensors may also be used in aircraft for “fly-by-feel” applications toprovide feedback to the flight controls to adjust the flight envelope orto limit loads in the flight pattern. Moreover, small sensors may beused with on-board wireless communication of controls on an aircraft,damage tolerant structures on an aircraft, and redundant power suppliesfor additional sources of power on an aircraft. The implementation ofsuch small sensors in these applications can require the use ofadditional power and communication wires which can increase thecomplexity and costs. Thus, generating power locally, rather than from acentral source, for these types of small sensor systems is desirable.

The harvesting of electricity from other forms of energy to drive smalland mid-size sensor devices (between 100 milliwatts and 100 watts) isknown. For example, solar panels have been used to harvest electricity.However, such solar panels can be costly to make and bulky in size. Inaddition, known power sources used with remote sensors can includevibration scavengers based on piezoelectric materials, which generate avoltage when deformed, and scavengers based on thermal gradients orthermoelectric junctions, which generate a voltage as a function oftemperature. However, these known power sources can be bulky, can addweight, and can be difficult to harvest sufficient energy at a specificlocation of need.

Thermoelectric based generator devices have been found to be effectivewhen used with aircraft and other craft because there are no movingparts and a thermal gradient is typically present. Thermoelectricdevices can convert thermal energy directly into electrical power orelectricity. The thermal gradient is applied across two faces of thedevice, as it is not sufficient to have a gradient across only one face.With thermoelectric devices, the power generated is dependent upon thechange in temperature across the device itself.

Known thermoelectric devices and systems include add-on componentsrather than fully integrated structures. For example, the use ofnon-integrated thermoelectric based generator devices that may includeexterior heat sinks and water cooling to increase the thermal gradientsis known. However, such non-integrated thermoelectric based generatordevices may not provide sufficient power for an extended period of timeand may be heavy, thus increasing the overall weight of an aircraft.Moreover, in applications where locally generated power is required, thethermal gradient accessible to an add-on device is typically only 1% to2%, resulting in the add-on device having decreased efficiency. Forexample, with an add-on device, only 1% of a 150° F. ΔT (temperaturedifference), or upwards of 250° F. ΔT on engine cowlings, or 2° F. ΔTcan be used to generate thermoelectric power. This may be improved byadding other heat conducting or cooling materials, but this can resultin the addition of significant weight, thus dropping the ratio ofgenerated power per pound of additional weight.

In addition, the use of add-on power sources, such as vibration basedenergy harvesting units, is also known. However, such vibration basedenergy harvesting units can add weight to the aircraft, and they canprotrude from the surrounding surface by ¼ inch to ½ inch, thusimpacting the ability to implement them. Moreover, the use of add-onsmall, thin-film lithium batteries to harvest energy is also known.However, such small, thin-film lithium batteries can require increasedmaintenance.

Accordingly, there is a need in the art for an integrated thermoelectriccomposite structure and method that provides advantages over knowndevices and methods.

SUMMARY

This need for an integrated thermoelectric composite structure andmethod is satisfied. Unlike known devices and methods, embodiments ofthe structure and method may provide numerous advantages discussed belowin the detailed description.

In an embodiment of the disclosure, there is provided a thermoelectriccomposite sandwich structure. The thermoelectric composite sandwichstructure comprises two prepreg composite face sheets and an integratedhoneycomb core assembled between the face sheets. The honeycomb corecomprises a plurality of core elements bonded together with a coreadhesive. Each core element has a first side substantially coated with anegative Seebeck coefficient conductive material having a plurality offirst spaced gaps. Further, each core element has a second sidesubstantially coated with a positive Seebeck coefficient conductivematerial having a plurality of second spaced gaps. The honeycomb corefurther comprises a plurality of electrical connections for connectingin series the coated first side to the coated second side. A temperaturegradient across the honeycomb core generates power.

In another embodiment of the disclosure, there is provided athermoelectric composite sandwich structure for use in aircraft andspacecraft. The thermoelectric composite sandwich structure comprisestwo prepreg composite face sheets and an integrated honeycomb coreassembled between the face sheets. The honeycomb core comprises aplurality of core elements selected from the group comprising corrugatedsheets and flat sheets, the core elements being bonded together with acore adhesive. Each core element has a first side substantially coatedwith a nickel layer having a plurality of first spaced gaps of a size inthe range of from about 0.01 inch to about 0.15 inch and spaced atintervals from each other in a range of about 0.150 inch to about 0.55inch. Each core element further has a second side substantially coatedwith an antimony layer having a plurality of second spaced gaps of asize in the range of from about 0.01 inch to about 0.15 inch and spacedat intervals from each other in a range of about 0.150 inch to about0.55 inch. The honeycomb core further comprises a plurality ofelectrical connections for connecting in series the nickel layer to theantimony layer. A temperature gradient across the honeycomb coregenerates power.

In another embodiment of the disclosure, there is provided a method formaking an integrated thermoelectric honeycomb core. The method comprisesproviding a corrugated core sheet. The method further comprisesdepositing a negative Seebeck coefficient conductive material with aplurality of first spaced gaps on a first side of the corrugated coresheet. The method further comprises depositing a positive Seebeckcoefficient conductive material with a plurality of second spaced gapson a second side of the corrugated core sheet. The method furthercomprises applying a core adhesive at intervals across a plurality ofdeposited corrugated core sheets. The method further comprisesassembling and bonding the plurality of deposited corrugated core sheetsto create an integrated thermoelectric honeycomb core. The methodfurther comprises electrically connecting deposited negative Seebeckcoefficient conductive material to deposited positive Seebeckcoefficient conductive material in an alternating pattern along a lengthof the integrated thermoelectric honeycomb core.

In another embodiment of the disclosure, there is provided a method formaking an integrated thermoelectric honeycomb core. The method comprisesproviding a flat core sheet. The method further comprises depositing anegative Seebeck coefficient conductive material with a plurality offirst spaced gaps on a first side of the flat core sheet. The methodfurther comprises depositing a positive Seebeck coefficient conductivematerial with a plurality of second spaced gaps on a second side of theflat core sheet. The method further comprises applying a core adhesiveat intervals across a plurality of deposited flat core sheets. Themethod further comprises assembling and bonding the plurality ofdeposited flat core sheets. The method further comprises expanding theplurality of deposited flat core sheets to create an integratedthermoelectric honeycomb core. The method further comprises electricallyconnecting deposited negative Seebeck coefficient conductive material todeposited positive Seebeck coefficient conductive material in analternating pattern along a length of the integrated thermoelectrichoneycomb core.

The features, functions, and advantages that have been discussed can beachieved independently in various embodiments of the disclosure or maybe combined in yet other embodiments further details of which can beseen with reference to the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be better understood with reference to the followingdetailed description taken in conjunction with the accompanying drawingswhich illustrate preferred and exemplary embodiments, but which are notnecessarily drawn to scale, wherein:

FIG. 1A is an illustration of an exploded perspective view of one of theembodiments of a thermoelectric composite sandwich structure of thedisclosure;

FIG. 1B is an illustration of a fully assembled perspective view of thethermoelectric composite sandwich structure of FIG. 1A;

FIG. 2 is an illustration of a top view of one of the embodiments of theintegrated thermoelectric honeycomb core of the disclosure;

FIG. 3A is an illustration of a side view of a first side of theintegrated thermoelectric honeycomb core of the disclosure;

FIG. 3B is an illustration of a side view of a second side of theintegrated thermoelectric honeycomb core of the disclosure;

FIG. 4A is an illustration of a corrugated core sheet used in formingone of the embodiments of the integrated thermoelectric honeycomb coreof the disclosure;

FIG. 4B is an illustration of a coated first side of the corrugated coresheet of FIG. 4A;

FIG. 4C is an illustration of a coated first side and a coated secondside of the corrugated core sheet of FIG. 4A;

FIG. 4D is an illustration of an assembled integrated thermoelectrichoneycomb core;

FIG. 5A is an illustration of a flat core sheet used in forming one ofthe embodiments of the integrated thermoelectric honeycomb core of thedisclosure;

FIG. 5B is an illustration of a coated first side of the flat core sheetof FIG. 5A;

FIG. 5C is an illustration of a coated first side and a coated secondside of the flat core sheet of FIG. 5A;

FIG. 5D is an illustration of assembled deposited flat core sheets;

FIG. 5E is an illustration of an expanded integrated thermoelectrichoneycomb core;

FIG. 6 is an illustration of a flow diagram of an embodiment of a methodof the disclosure for making one of the embodiments of the integratedthermoelectric honeycomb core of the disclosure; and,

FIG. 7 is an illustration of a flow diagram of another embodiment of amethod of the disclosure for making one of the embodiments of theintegrated thermoelectric honeycomb core of the disclosure.

DETAILED DESCRIPTION

Disclosed embodiments will now be described more fully hereinafter withreference to the accompanying drawings, in which some, but not all ofthe disclosed embodiments are shown. Indeed, several differentembodiments may be provided and should not be construed as limited tothe embodiments set forth herein. Rather, these embodiments are providedso that this disclosure will be thorough and complete and will fullyconvey the scope of the disclosure to those skilled in the art.

The disclosure provides for embodiments of an integrated thermoelectriccomposite sandwich structure having an integrated thermoelectrichoneycomb core and a method for making the same. Embodiments of thestructure and method may be used in aircraft, spacecraft, motorcraft,watercraft, and other craft, as well vehicles and structures. Inaddition, embodiments of the structure and method may be used withintegrated commercial building materials for both cooling applications,as well as energy harvesting from lightweight structures.

FIG. 1A is an illustration of an exploded perspective view of one of theembodiments of an integrated thermoelectric composite sandwich structure10 of the disclosure. FIG. 1B is an illustration of a fully assembledperspective view of the integrated thermoelectric composite sandwichstructure 10 of FIG. 1A. In one of the embodiments of the disclosure,there is provided the integrated thermoelectric composite sandwichstructure 10. The integrated thermoelectric composite sandwich structure10 comprises a first face sheet 12 having an interior side 14 and anexterior side 16. The integrated thermoelectric composite sandwichstructure 10 further comprises a second face sheet 18 having an interiorside 20 and an exterior side 22. Preferably, the first face sheet 12 andthe second face sheet 18 are comprised of a prepreg composite material.Suitable prepreg composite materials may comprise carbon fabric,fiberglass, quartz, aromatic aramid and polyamide preimpregnated withresin, or another suitable prepreg composite material. The first facesheet 12 and the second face sheet 18 may also be comprised of metalmaterials, such as aluminum or another suitable metal, plastic materialssuch as polyimide or another suitable plastic, or another suitablematerial. The thickness of the first and second face sheets 12, 18 maypreferably be from about 0.005 inch to about 0.1 inch thick or ofanother suitable thickness. The integrated thermoelectric compositesandwich structure 10 further comprises an integrated thermoelectrichoneycomb core 24 assembled between the first face sheet 12 and thesecond face sheet 18. The honeycomb core 24 has a first end 26 adjacentthe interior side 14 of the first face sheet 12. The honeycomb core 24has a second end 28 adjacent the interior side 20 of the second facesheet 19. The honeycomb core 24 has first sides 30 and second sides 32.The honeycomb core 24 may comprise cells 33 having a hexagonal shape.Hexagonal cells provide a minimum density for a given amount of materialcomprising the honeycomb core. Alternatively, the honeycomb core maycomprise cells having another suitable shape.

FIG. 2 is an illustration of a top view of one of the embodiments of theintegrated thermoelectric honeycomb core 24 of the disclosure. As shownin FIG. 2, the honeycomb core 24 comprises a plurality of core elements25. In one embodiment the core element 25 may comprise a corrugated coresheet 64 (see FIG. 4A). In another embodiment the core element 25 maycomprise a flat core sheet 70 (see FIG. 5A). However, other suitablecore elements 25 may also be used. The core elements 25 may be made offiberglass, plastic, paper, carbon or aramid fiber, reinforcedpreimpregnated resin coated sheets or paper, or another suitablematerial. The thickness of the core element 25 may preferably be from0.3 inch to 2.0 inches thick or of another suitable thickness. Theplurality of core elements 25 may preferably be bonded together with acore adhesive 46. The core adhesive 46 may comprise an epoxy, othersimilar resins, or another suitable adhesive. Each core element 25 has afirst side 30 and a second side 32. Each first side 30 is substantiallycoated with a negative Seebeck coefficient conductive material 34. Thenegative Seebeck coefficient conductive material 34 preferably comprisesnickel (−15 μV·K⁻¹), bismuth (−72 μV·K⁻¹), constantan (−35 μV·K⁻¹),potassium (−9 μV·K⁻¹), or another suitable negative Seebeck coefficientconductive material. More preferably, the negative Seebeck coefficientconductive material 34 is nickel. The conductive material may comprisefoil or deposited metallic film layers deposited via thermal deposition,vapor deposition, chemical vapor deposition, plating, sputtering, orother suitable deposition processes, or the conductive material maycomprise another suitable material. The thickness of the metallic filmlayer may be in the range of from about 0.05 mil thick to about 5.0 milthick. The negative Seebeck coefficient conductive material 34 may bedeposited onto the first side 30 via a suitable deposition process, suchas thermal deposition, vapor deposition, chemical vapor deposition,plating, sputtering or other deposition processes. If the negativeSeebeck coefficient conductive material 34 is deposited, the negativeSeebeck coefficient conductive material 34 preferably has a plurality offirst spaced gaps 36. The first spaced gaps 36 are preferably of a sizein the range of from about 0.01 inch to about 0.15 inch and arepreferably spaced at intervals from each other in a range of about 0.15inch to about 0.55 inch. However, the first spaced gaps 36 may be ofother suitable sizes and may be spaced apart from each other at othersuitable intervals, depending on the size of the core element 25 used.If the negative Seebeck coefficient conductive material coating 34 isdeposited as a contiguous sheet or applied as a contiguous foil layer,the first spaced gaps 36 may be precision machined into the metallicfilm layer by an etching process or another suitable removal process.

As shown in FIG. 2, each second side 32 of each core element 25 issubstantially coated with a positive Seebeck coefficient conductivematerial 38. The positive Seebeck coefficient conductive material 38preferably comprises antimony (47 μV·K⁻¹), iron (19 μV·K⁻¹), copper (6.5V·K⁻¹), silver (6.5 μV·K⁻¹), nichrome (25 μV·K⁻¹), or another suitablepositive Seebeck coefficient conductive material. More preferably, thepositive Seebeck coefficient conductive material 38 is antimony. Thepositive Seebeck coefficient conductive material 38 may be depositedonto the second side 32 via a suitable deposition process, such asthermal deposition, vapor deposition, chemical vapor deposition,plating, sputtering, or other deposition processes. If the positiveSeebeck coefficient conductive material 38 is deposited, the positiveSeebeck coefficient conductive material 38 preferably has a plurality ofsecond spaced gaps 40. The second spaced gaps 40 are preferably of asize in the range of from about 0.01 inch to about 0.15 inch and arepreferably spaced at intervals from each other in a range of about 0.15inch to about 0.55 inch. However, the second spaced gaps 40 may be ofother suitable sizes and may be spaced apart from each other at othersuitable intervals, depending on the size of the core element 25 used.If the positive Seebeck coefficient conductive material 38 is depositedas a contiguous sheet or applied as a contiguous foil layer, the secondspaced gaps 40 may be precision machined into the metallic film layer byan etching process or another suitable removal process.

The honeycomb core 24 may be constructed by depositing internally withinthe thermoelectric composite sandwich structure 10 and across the widthof the honeycomb core 24 with alternating negative Seebeck coefficientconductive material 34 and positive Seebeck coefficient conductivematerial 38 connected in series, such that a temperature gradient acrossthe honeycomb core 24 generates power. As shown in FIG. 2, the honeycombcore 24 further comprises a plurality of continuous electricalconnections 48 and a plurality of discontinuous electrical connections50 for connecting in series the first side 30 of each core element 25 tothe second side 32 of each core element 25. Sections 54 of the honeycombcore 24 may be connected with a series style connection 52 having avoltage load 56. The alternating negative Seebeck coefficient conductivematerial 34, such as nickel, and the positive Seebeck coefficientconductive material 38, such as antimony, connected in series, create aplurality of nickel-antimony based thermopiles connected electrically inseries and thermally in parallel. For purposes of this application, athermopile means an electronic device that converts thermal energy intoelectrical energy, and it is composed of thermocouples connected inseries or in parallel. Thermopiles do not measure the absolutetemperature but generate an output voltage proportional to a localtemperature difference or temperature gradient.

FIG. 3A is an illustration of a side view of first side 30 of thethermoelectric composite sandwich structure 10 of the disclosure. FIG.3A shows the first side 30 of the honeycomb core 24 between the firstface sheet 12 and the second face sheet 18. The first side 30 issubstantially coated with the negative Seebeck coefficient conductivematerial 34 and preferably has the plurality of first spaced gaps 36spaced at intervals along the first side 30. In this embodiment of thethermoelectric composite sandwich structure 10, portions 42 of thepositive Seebeck coefficient conductive material 38 may be wrappedaround from the second side 32 (see FIG. 3B) to the first side 30.Honeycomb core node lines 58 are shown and such node lines may comprisesstrips of adhesive that bond the corrugated core sheets 64 (see FIG. 4D)or the flat core sheets 70 (see FIG. 5E) together.

FIG. 3B is an illustration of a side view of second side 32 of thethermoelectric composite sandwich structure 10. FIG. 3B shows the secondside 32 of the honeycomb core 24 between the first face sheet 12 and thesecond face sheet 18. The second side 32 is substantially coated withthe positive Seebeck coefficient conductive material 38 and preferablyhas the plurality of second spaced gaps 40 spaced at intervals along thesecond side 32. In this embodiment of the thermoelectric compositesandwich structure 10, portions 44 of the negative Seebeck coefficientconductive material 36 may be wrapped around from the first side 30 (seeFIG. 3A) to the second side 32. Honeycomb core node lines 58 are alsopresent on the second side 32. A temperature gradient (ΔT) 60 (see FIG.3A) across the honeycomb core 24 on the first side 30 generates power. Atemperature gradient (ΔT) 62 (see FIG. 3B) across the honeycomb core 24on the second side 32 also generates power. Preferably, 98% of thetemperature gradient across the honeycomb core 24 generates power.

Fabrication of the integrated thermoelectric honeycomb core 24 maycomprise several method embodiments. In one method, as shown in FIGS.4A-4D and FIG. 6, the core element 25 comprises the corrugated coresheet 64. In another method, as shown in FIGS. 5A-5E and FIG. 7, thecore element 25 comprises the flat core sheet 70. Other suitable methodsof fabrication of the honeycomb core 24 using other suitable coreelements 25 may also be used.

FIG. 6 is an illustration of a flow diagram of an embodiment of a method100 of the disclosure for making one of the embodiments of theintegrated thermoelectric honeycomb core 24 of the disclosure using thecorrugated core sheet 64. The method 100 comprises step 102 forproviding a corrugated core sheet 64 (see FIG. 4A). FIG. 4A is anillustration of the corrugated core sheet 64 used in forming one of theembodiments of the integrated thermoelectric honeycomb core 24. Themethod 100 further comprises step 104 of depositing the negative Seebeckcoefficient conductive material 34 (see FIG. 4B) with a plurality offirst spaced gaps 36 on the first side 30 of the corrugated core sheet64. FIG. 4B is an illustration of a coated first side 30 of thecorrugated core sheet 64 of FIG. 4A. The negative Seebeck coefficientconductive material 34 preferably comprises nickel, bismuth, constantan,potassium, or another suitable negative Seebeck coefficient conductivematerial. More preferably, the negative Seebeck coefficient conductivematerial 34 comprises nickel. The conductive material is preferably foilor another suitable material. The negative Seebeck coefficientconductive material 34 may be deposited onto the first side 30 via asuitable deposition process, such as thermal deposition, vapordeposition, chemical vapor deposition, plating, sputtering, or otherdeposition processes. The first spaced gaps 36 may comprise patternedbreak points around alternating edges 66 on the first side 30 of thecorrugated core sheet 64. The first spaced gaps 36 are preferably of asize in the range of from about 0.01 inch to about 0.15 inch and arepreferably spaced at intervals from each other in a range of about 0.15inch to about 0.55 inch. However, the first spaced gaps 36 may be ofother suitable sizes and may be spaced apart from each other at othersuitable intervals, depending on the size of the corrugated core sheet64 used.

The method 100 further comprises step 106 of depositing the positiveSeebeck coefficient conductive material 38 with a plurality of secondspaced gaps 40 on the second side 32 of the corrugated core sheet 64(see FIG. 4C). FIG. 4C is an illustration of a coated first side 30 anda coated second side 32 of the corrugated core sheet 64 of FIG. 4A. Thepositive Seebeck coefficient conductive material 38 preferably comprisesantimony, iron, a mixture of copper and silver, nichrome, or anothersuitable positive Seebeck coefficient conductive material. Morepreferably, the positive Seebeck coefficient conductive material 38comprises antimony. The conductive material may comprise foil ordeposited metallic film layers deposited via thermal deposition, vapordeposition, chemical vapor deposition, plating, sputtering, or othersuitable deposition processes, or the conductive material may compriseanother suitable material. The positive Seebeck coefficient conductivematerial 38 may be deposited onto the second side 32 via a suitabledeposition process, such as thermal deposition, vapor deposition,chemical vapor deposition, plating, sputtering, or other depositionprocesses. The second spaced gaps 40 may comprise patterned break pointsaround alternating edges 68 on the second side 32 of the corrugated coresheet 64. The second spaced gaps 40 are preferably of a size in therange of from about 0.01 inch to about 0.15 inch and are preferablyspaced at intervals from each other in a range of about 0.15 inch toabout 0.55 inch. However, the second spaced gaps 40 may be of othersuitable sizes and may be spaced apart from each other at other suitableintervals, depending on the size of the corrugated core sheet 64 used.

The method 100 further comprises step 108 of applying a core adhesive 46(see FIG. 4D) at intervals across a plurality of deposited corrugatedcore sheets 64. The core adhesive 46 may comprise an epoxy, othersimilar resins, or another suitable adhesive. The method 100 furthercomprises step 110 of assembling and bonding the plurality of depositedcorrugated core sheets 64 to create the integrated thermoelectrichoneycomb core 24. FIG. 4D is an illustration of the assembledthermoelectric honeycomb core 24. The method 100 further comprises step112 of electrically connecting with continuous electrical connections 48(see FIG. 2) and discontinuous electrical connections 50 (see FIG. 2)the deposited negative Seebeck coefficient conductive material 34 to thedeposited positive Seebeck coefficient conductive material 38 in analternating pattern along a length of the integrated thermoelectrichoneycomb core. Sections 54 of the integrated thermoelectric honeycombcore 24 may be connected with a series style connection 52 having avoltage load 56 (see FIG. 2). The electrically connecting step 112 ofelectrically connecting the deposited negative Seebeck coefficientconductive material to the deposited positive Seebeck coefficientconductive material may also be performed prior to both the applying ofthe core adhesive step 108 and the assembling and bonding of theplurality of deposited corrugated core sheets step 110.

FIG. 7 is an illustration of a flow diagram of another embodiment of amethod 200 of the disclosure for making one of the embodiments of theintegrated thermoelectric honeycomb core 24 of the disclosure using theflat core sheet 70. The method 200 comprises step 202 of providing theflat core sheet 70 (see FIG. 5A). FIG. 5A is an illustration of the flatcore sheet 70 used in forming one of the embodiments of the integratedthermoelectric honeycomb core 24. The method 200 further comprises step204 of depositing negative Seebeck coefficient conductive material 34with a plurality of first spaced gaps 36 on the first side 30 of theflat core sheet 70. FIG. 5B is an illustration of a coated first side ofthe flat core sheet 70 of FIG. 5A. The negative Seebeck coefficientconductive material 34 preferably comprises nickel, bismuth, constantan,potassium, or another suitable negative Seebeck coefficient conductivematerial. Preferably, the negative Seebeck coefficient conductivematerial 34 comprises nickel. The conductive material may comprise foilor deposited metallic film layers deposited via thermal deposition,vapor deposition, chemical vapor deposition, plating, sputtering, orother suitable deposition processes, or the conductive material maycomprise another suitable material. The deposition process may comprisea suitable deposition process such as thermal deposition, vapordeposition, chemical vapor deposition, plating, sputtering, or otherdeposition processes. The first spaced gaps 36 are preferably of a sizein the range of from about 0.01 inch to about 0.15 inch and arepreferably spaced at intervals from each other in a range of about 0.15inch to about 0.55 inch. However, the first spaced gaps 36 may be ofother suitable sizes and may be spaced apart from each other at othersuitable intervals, depending on the size of the flat core sheet 70used.

The method 200 further comprises step 206 of depositing positive Seebeckcoefficient conductive material 38 with a plurality of second spacedgaps 40 on second side 32 of the flat core sheet 70. FIG. 5C is anillustration of coated first side 30 and coated second side 32 of theflat core sheet 70 of FIG. 5A. The positive Seebeck coefficientconductive material 38 preferably comprises antimony, iron, a mixture ofcopper and silver, nichrome, or another suitable positive Seebeckcoefficient conductive material. More preferably, the positive Seebeckcoefficient conductive material 38 comprises antimony. The conductivematerial is preferably foil or another suitable material. The depositionprocess may comprise a suitable deposition process such as thermaldeposition, vapor deposition, chemical vapor deposition, plating, oranother deposition process. The second spaced gaps 40 are preferably ofa size in the range of from about 0.01 inch to about 0.15 inch and arepreferably spaced at intervals from each other in a range of about 0.15inch to about 0.55 inch. However, the second spaced gaps 40 may be ofother suitable sizes and may be spaced apart from each other at othersuitable intervals, depending on the size of the flat core sheet 70used.

The method 200 further comprises step 208 of applying core adhesive 46at intervals across a plurality of deposited flat core sheets 70. Thecore adhesive 46 may comprise an epoxy, other similar resins, or anothersuitable adhesive. The method 200 further comprises step 210 ofassembling and bonding the plurality of deposited flat core sheets 70.FIG. 5D is an illustration of the assembled flat core sheets 70 of theintegrated thermoelectric honeycomb core 24. The method 200 furthercomprises step 212 of expanding the plurality of deposited flat coresheets 70 to create the integrated thermoelectric honeycomb core 24.FIG. 5E is an illustration of the expanded integrated thermoelectrichoneycomb core 24. The method 200 further comprises step 214 ofelectrically connecting with continuous electrical connections 48 (seeFIG. 2) and discontinuous electrical connections 50 (see FIG. 2) thedeposited negative Seebeck coefficient conductive material 34 to thedeposited positive Seebeck coefficient conductive material 38 in analternating pattern along a length of the integrated thermoelectrichoneycomb core. Sections 54 of the integrated thermoelectric honeycombcore 24 may be connected with a series style connection 52 having avoltage load 56 (see FIG. 2). The electrically connecting step 214 ofelectrically connecting the deposited negative Seebeck coefficientconductive material to the deposited positive Seebeck coefficientconductive material may also be performed prior to both the applying ofthe core adhesive step 208 and the assembling and bonding of theplurality of deposited flat core sheets step 210. In addition, theelectrical connections may be made at the individual flat core sheet 70level or once the integrated thermoelectric honeycomb core 24 has beenexpanded. One or more end electrical connections 72 (see FIG. 2) may bemade prior to the expanding step 212 if desired. The end electricalconnections 72 preferably connect one or more negative Seebeckcoefficient conductive materials 34 to one or more positive Seebeckcoefficient conductive materials 38. The end electrical connections 72may be soldered, tack welded, bonded with a conductive adhesive such asepoxy, or connected in another suitable manner to the one or morenegative Seebeck coefficient conductive materials 34 and to the one ormore positive Seebeck coefficient conductive materials 38.

The embodiments of the thermoelectric composite sandwich structure 10with the integrated thermoelectric honeycomb core 24 and embodiments ofthe method for making the same have numerous advantages. Thethermoelectric composite sandwich structure 10 fully integratesthermoelectric elements (i.e., the deposited negative Seebeckcoefficient conductive material and the deposited positive Seebeckcoefficient conductive material) within a non-metallic cellularhoneycomb core formed in a sandwich structure to generate energy. Theintegrated thermoelectric honeycomb core 24 disclosed herein caninternally generate power without moving parts and without maintenancefor embedded sensors. Embodiments of the structure and method disclosedherein enable fully embedded structural health monitoring (SHM), as thepower or energy can be generated, sensors can be used, and the signalscan be transmitted all from within the honeycomb core internal powersource, thus minimizing punctures or holes in the first and second facesheets 12, 18. By generating power with the honeycomb core structure,embodiments of the structure and method disclosed herein can enablestructural health monitoring (SHM) of joints, data collection andtransmission units, bonded structure, and assessment of core health, andcan lead to the implementation of fully bonded structure, fly-by-feeltechnologies, on-board wireless communication of controls, damagetolerant structures, and redundant power supplies for additional sourcesof power on an aircraft, spacecraft, or other craft.

Further advantages of embodiments of the structure and method disclosedherein include decreased costs or cost avoidance for power generationfor structural health monitoring (SHM) type applications, reduced damageimpact, reduced inspection cycles, lower installation costs of remotehardware, and decreased weight and complexity by not having to powerremote sensors and use additional communication wires. In addition,embodiments of the structure and method disclosed herein provide forgeneration of power from structural components which are exposed tothermal gradients, and may provide more than a few hundred watts ofpower from large areas exposed to appropriate temperature gradients. Useof embodiments of the structure and method disclosed herein withstructures used in space creates a natural thermal gradient across thehoneycomb core structure and can be used as a means of generating powerwithout having to use solar arrays. Further, embodiments of thestructure and method disclosed herein may be used to cool the facesheets 12, 18, enabling the integrated thermoelectric structure toprovide for environmental control. In other applications, embodiments ofthe structure and method disclosed herein can be used to powersatellites and other spacecraft.

The integrated thermoelectric honeycomb core structure incorporates aplurality of thermopiles in series which are supported on either side ofthe honeycomb core between the composite sandwich face sheets 12, 18. Byusing metallic coatings with extreme Seebeck coefficients to overcomethe electrical loss concerns, taking advantage of the increased areaprovided through the fully integrated honeycomb core structure, and thelimited weight gains induced by the large area, embodiments of a methodto internally generate power within structural material may be obtained.In space, the thermal gradient of the structure disclosed herein canalso be used to harness thermal gradients generated from solar flux,perhaps even from the structural supports for solar cells. In 0.6 inchthick core structures radiating into space, with 1.0 sun flux(approximately 1.4 kW·m⁻² (kilo-watt meter)), the first and second facesheet 12, 18 temperatures rise to 242.2° F., whereas the shielded sideof the honeycomb core remains at approximate 40° F., creating a 200° F.ΔT (temperature gradient or drop) across the honeycomb core. This can bedirectly harvested with embodiments of the structure and methoddisclosed herein for additional energy harvesting from the structuralelements.

Ninety-eight percent (98%) of the thermal gradient across the integratedthermoelectric honeycomb core structure may be harvested for powergeneration using the integrated thermoelectric composite sandwichstructure disclosed herein, whereas only 1% to 2% of the thermalgradient may be used in known non-integrated or add-on devices. Even ifthe efficiencies of the integrated thermoelectric composite sandwichstructure are one quarter of known devices, they are approximatelytwenty-five (25) times more efficient at harvesting energy from thetemperature gradient present across the honeycomb core structure. Forexample, using an integrated approach, for one (1) ounce of material,0.5 watts can be generated with a ΔT (temperature gradient) of 250° F.(Fahrenheit). Using known devices, however, the same amount of power canrequire approximately 25 ounces of additional material, which is notpractical for such a small amount of power. At the crux of the disclosedembodiments are a number of nickel-antimony based thermopiles, connectedelectrically in series and thermally in parallel. Each thermopile cangenerate a voltage of 50-60 μV·K⁻¹ (microvolt per degree Kelvin). Attypical temperature gradients seen on board aircraft and air vehicles,this can amount to approximately 7.5 mV to 10 mV (millivolt) perthermopile. Connecting one hundred fifty (150) in series provides anapproximately 1.5V (volt) potential. Assuming a core thickness ofapproximately 0.6 inch (typical in engine cowlings), a 2 mil thick foil(or plating) for both metals, with 0.5 inch wide thermopile,approximately upwards of 1.0 amp (ampere) of current can be produced. Aone square foot structure of 150 thermopiles can generate approximately1.0 amp at 1 volt. This can require one (1) additional ounce of material(the mass of metal), and can be more than sufficient to power a largeembedded sensor array for use in structural health monitoring (SHM).Reduction of the size of materials in all dimensions may be possiblethrough optimization for various applications. Calculations have beenperformed to assess feasibility of the disclosed embodiments herein andpotential efficiencies. Embodiments of the structure disclosed hereincan provide approximately 25 W·lbs⁻¹ (watt pounds) with known materials,and refinements of embodiments of the structure and optimization of thematerials disclosed herein may provide upwards of 100 W·lbs⁻¹. In someapplications with the integrated thermoelectric honeycomb core structuredisclosed herein, the available ΔT is much smaller at one face sheet(only 1% of the ΔT), so in such applications, the integrated approach isapproximately 25 times more efficient than known non-integratedapproaches.

Many modifications and other embodiments of the disclosure will come tomind to one skilled in the art to which this disclosure pertains havingthe benefit of the teachings presented in the foregoing descriptions andthe associated drawings. The embodiments described herein are meant tobe illustrative and are not intended to be limiting or exhaustive.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

What is claimed is:
 1. A method for making an integrated thermoelectrichoneycomb core, comprising: providing a corrugated core sheet with afirst face and a second face, the first and second faces comprisingopposing sides of the corrugated core sheet; depositing a negativeSeebeck coefficient conductive material with a plurality of first spacedgaps on the first face of the corrugated core sheet; depositing apositive Seebeck coefficient conductive material with a plurality ofsecond spaced gaps on the second face of the corrugated core sheet,wherein the first face gaps on the first face of the corrugated coresheet do not overlap with the second face gaps on the second face of thecorrugated core sheet; applying a core adhesive at intervals across aplurality of deposited corrugated core sheets; assembling and bondingthe plurality of deposited corrugated core sheets to create anintegrated thermoelectric honeycomb core, wherein the first face of eachof the plurality of corrugated core sheets faces the second face of eachadjacent corrugated core sheet of the plurality of corrugated coresheets to form a honeycomb shape when assembled and the positive Seebeckcoefficient conductive material and negative Seebeck coefficientmaterials alternate on the opposing sides of the plurality of corrugatedcore sheets; and, electrically connecting deposited negative Seebeckcoefficient conductive material to deposited positive Seebeckcoefficient conductive material in an alternating pattern along a lengthof the first and second faces of the integrated thermoelectric honeycombcore, wherein the conductive material is a foil or deposited metallicfilm layers.
 2. The method of claim 1 wherein the electricallyconnecting deposited negative Seebeck coefficient conductive material todeposited positive Seebeck coefficient conductive material can beperformed prior to the applying the core adhesive and assembling andbonding the plurality of deposited corrugated core sheets.
 3. The methodof claim 1 wherein the first spaced gaps and the second spaced gaps areof a size in the range of from about 0.01 inch to about 0.15 inch andare spaced at respective intervals from each other in a range of about0.15 inch to about 0.55 inch.
 4. The method of claim 1 wherein thenegative Seebeck coefficient conductive material is selected from thegroup comprising nickel, bismuth, constantan, and potassium.
 5. Themethod of claim 1 wherein the positive Seebeck coefficient conductivematerial is selected from the group comprising antimony, iron, a mixtureof copper and silver, and nichrome.
 6. The method of claim 1 furthercomprising integrating the integrated thermoelectric honeycomb core in abonded structure on an aircraft or a spacecraft.
 7. A method for makingan integrated thermoelectric honeycomb core comprising: providing a flatcore sheet with first and second faces that are the opposing planarsides of the flat core sheet; depositing a negative Seebeck coefficientconductive material with a plurality of first spaced gaps on the firstface of the flat core sheet; depositing a positive Seebeck coefficientconductive material with a plurality of second spaced gaps on the secondface of the flat core sheet, wherein the gaps on the first face of thecorrugated core sheet do not overlap with the gaps on the second face ofthe corrugated core sheet; applying a core adhesive at intervals acrossa plurality of deposited flat core sheets; assembling and bonding theplurality of deposited flat core sheets wherein the first and secondfaces of the plurality of flat core sheets oppose each other whenassembled and the positive Seebeck coefficient conductive material andnegative Seebeck coefficient materials alternate on the opposing sidesof the plurality of flat core sheets; expanding the plurality ofdeposited flat core sheets to create an integrated thermoelectrichoneycomb core; and, electrically connecting deposited negative Seebeckcoefficient conductive material to deposited positive Seebeckcoefficient conductive material in an alternating pattern along a lengthof the first and second faces of the integrated thermoelectric honeycombcore, wherein the conductive material is foil or deposited metallic filmlayers.
 8. The method of claim 7 wherein the electrically connectingdeposited negative Seebeck coefficient conductive material to depositedpositive Seebeck coefficient conductive material can be performed priorto the applying the core adhesive and assembling and bonding theplurality of deposited flat core sheets.
 9. The method of claim 7wherein the first spaced gaps and the second spaced gaps are of a sizein the range of from about 0.01 inch to about 0.15 inch and are spacedat respective intervals from each other in a range of about 0.15 inch toabout 0.55 inch.
 10. The method of claim 7 wherein the negative Seebeckcoefficient conductive material is selected from the group comprisingnickel, bismuth, constantan, and potassium.
 11. The method of claim 7wherein the positive Seebeck coefficient conductive material is selectedfrom the group comprising antimony, iron, a mixture of copper andsilver, and nichrome.
 12. The method of claim 7 further comprisingintegrating the integrated thermoelectric honeycomb core in a bondedstructure on an aircraft or a spacecraft.